The invasive species situation in Florida is severe, and when one considers the climatic, demographic, and environment situation in Florida, the severity of the problem is even greater than at first glance. The breadth of invasive land animals in Florida that arguably merit eradication, or at least control, is extensive. The list is extremely varied and includes animals ranging from unusual species of distant origins to more recognizable invaders brought in from other states in the U.S., as well as feral domestics. A variety of steps have been taken to reduce the number of introductions, with some apparent success (Hardin 2007). As is often stated (e.g., NISC 2001), prevention is the most efficient and economical means to eliminate exotic species. However, even if no new exotic vertebrates become established in Florida, there is an abundance of established exotic vertebrates that merit management action.
A brief sampling of Florida's invasive species originating from other parts of the globe (besides those detailed already) include species such as the common boa (Boa constrictor), Cuban treefrog (Osteopilus septentrionalis), green iguana (Iguana iguana), black and white tegu (Tupinambis merianae), peafowl (Pavo cristatus), spectacled caiman (Caiman crocodilus), monk parakeet (Myiopsitta monachus), rhesus monkey (Macaca mulatta), sacred ibis (Threskiornis aethiopicus). Species native to the U.S., but exotic in Florida include animals such as coyotes (Canis latrans), red fox (Vulpes vulpes), black-tailed prairie dogs (Cynomys ludovicianus), red-eared slider (Trachemys scripta elegans) and armadillos (Dasypus novemcinctus), while other feral domestics widespread in Florida besides swine and cats include goats (Capra hirus) and dogs (Canis familiaris). Many other less noticeable species have become established in Florida, and other species are suspected to be breeding there, but without firm documentation. Not all will be subjected to eradication or control, but some of the invaders could present potentially severe environmental, human health, and/or economic consequences if their populations are not controlled or eradicated.
Species such as Gambian giant pouched rats, Nile monitors, ctenosaurs, Burmese pythons and many of the other exotic species represent novel species to be considered for eradication or control. The Gambian giant pouched rat, purple swamphen and black-tailed jackrabbit are examples of how necessary incentive and resources can be applied to directly design and implement a practical eradication or control program (Engeman et al. 2006, 2007a). Too often, invasive species merely become the subjects of biological and population studies (e.g., Campbell 2007), but there is a limit at some point to the utility in conducting biological studies of introduced species unless the results directly assist in their removal (e.g., Donlan et al. 2003, Simberloff 2003, Campbell 2007). Donlan et al. (2003) concluded that research directly facilitating eradication tools and projects should be of high priority. Developing the information and technologies from which control strategies can be developed and implemented is an essential component to addressing many invasive species situations. Equally important is the development of public and governmental motivation, i.e. funding, to manage invasive species before their populations expand beyond feasible control.
Many of the problematic invasive vertebrates in Florida are predators. Predation not only threatens many rare species (Hecht and Nickerson, 1999), but the deleterious impacts of predation losses is compounded by habitat loss (Reynolds and Tapper, 1996). Predators also increase the risk of catastrophic extinction of prey populations (Schoener et al. 2001). Given the amount of habitat lost to development in Florida and the state's proclivity for catastrophic hurricanes (two circumstances magnified on the Keys and other islands), a number of species in Florida are at high risk. Since alien predators are more dangerous than native predators to prey populations (Salo et al. 2007), the impacts from invasive predators, whether small like northern curlytail lizards or large like Burmese pythons, could have devastating impacts on Florida's native species, especially the listed rare species.
For a number of well-established species in Florida, such as feral swine, feral cats and green iguanas, there is no practical means to eradicate them from the state. That does not mean they cannot be intensively controlled, managed, or eradicated in situations of greatest priority on a localized scale, especially islands. For example, feral swine are ubiquitous and destructive, but as already discussed, would never be considered for state-wide eradication. However, swine have been successfully targeted in a nearly-completed eradication effort on Cayo Costa and Punta Blanca Islands, with concomitant dramatic improvements in nesting by listed sea turtles and shorebirds. Species like the black-tailed jackrabbit, Gambian giant pouched rat and purple swamphen were identified as feasible, practical, and valuable to eradicate before they become too deeply entrenched across a broad range. To that end, Parkes and Murphy (2003) delineated some "obligate rules" for successful eradication: 1) all individuals of the target species must be at risk of being killed, 2) target species must be removed at a rate greater than the rate they replace their losses, and 3) the risk of immigration must be zero. Given suitable control methods applied in a systematic and sustained integrated pest management program, these criteria could well be met for a number of invasive species in Florida, if their populations are not permitted to fester into an unmanageable situation. The case of the black-tailed jackrabbit demonstrates that, even with many political gyrations, a population of a species with a restricted range can be eradicated without an excessive outlay of resources (Engeman 2007a). To leave such a situation unaddressed is like leaving a slow-burning fuse lit to an ecological bomb.
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